For the First Time, Scientists Have Tunneled Sound Through a Vacuum
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Because space is a vacuum nearly devoid of particles, sound can’t travel through its vast emptiness.
However, scientists from the University of Jyväskylä in Finland have successfully “tunneled” sound through such a vacuum via an electromagnetic effect.
Although this experiment seems to flout the idea of space’s silent nature, this “tunneling” can only occur over extremely small distances.
“In space, no one can hear you scream.”
It’s a brilliant tagline for a horror film set in space, as this inaudible concept is both terrifying and scientifically true. Sound waves (also known as “acoustic phonons”) require particles to travel—whether through air, water, or some other medium—and the vacuum of space doesn’t have nearly enough particles to transmit sound. In other words, it’s the perfect hunting grounds for an acid-spewing, human-hungry xenomorph.
However, Alien’s macabre motto now comes with an asterisk. Scientists from the University of Jyväskylä in Finland successfully “tunneled” sound through a vacuum gap between two solids—specifically, two zinc oxide crystals.
“[Sound waves] do not exist in vacuum, leading to the initial conclusion that it is impossible for the vacuum to transmit the energy of an acoustic wave between two separated media,” the researchers write in a study published this week in the journal Communications Physics. “However, at the atomic scale the vibrations of the nuclei can propagate via their electrical interactions through vacuum. Thus, a question can be raised, whether acoustic phonons can also be transmitted across larger than atomic scale vacuum gaps through some electromagnetic mechanism.”
These crystals are both piezoelectric, meaning that they produce electricity when they experience heat or a mechanical stress. In this case, this includes sound. Because electricity can exist in a vacuum, the sound can actually jump—or tunnel—from one crystal to another.
This “tunneling” occurs in frequencies in our audible range (such as a human scream, perhaps) as well as ultrasonic and hypersonic frequencies beyond human hearing. Of course, there is one big catch—the distance between these two crystals can’t be larger than the wavelength of the sound wave itself. So, as frequencies increase, the gap between the two crystals must get smaller and smaller.
This method of sound “tunneling” also isn’t perfect. Sometimes, sound waves were warped, reflected, or otherwise distorted as it traveled via this electric field. However, on other occasions, the sound waves survived the microscopic vacuum journey unaffected.
“In most cases the effect is small, but we also found situations where the full energy of the wave jumps across the vacuum with 100% efficiency, without any reflections,” Ilari Maasilta from the Nanoscience Center at the University of Jyväskylä and study co-author said in a press statement. “As such, the phenomenon could find applications in microelectromechanical components (smartphone technology) and in the control of heat.”
In other words, the xenomorph can maintain its advantage.
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